1. Field of the Invention
The instant disclosure relates to a light emitting device; in particular, to a light emitting device with a light-uniforming anti-glaring structure.
2. Description of Related Art
Light emitting diode (LED), having the advantage of being energy efficient and long lasting, is the inevitable source for lighting in the foreseeable future. However, LED is a spot light source that generates focused light output and therefore easily leads to user discomfort due to direct glare formed from excessive brightness, especially in cases when such light source is utilized as a table lamp. Furthermore, whether traditional light source or other prior LED module all possesses issues of direct glare or reflective glare, which affects the viewing comfort of users when observing objects under such lighting condition. For table lamps, there are 3 types of common glares: direct glare, contract glare, and reflective glare. Direct glare is caused by directly viewing a focused and intense light source, such as directly looking at the sun during day-time, an incoming car lamp during night-time, or a light tube while reading with a table lamp. Contrast glare is caused by excessive difference of lighting ratio from two difference light source, such as a table lamp and a ceiling lamp. Reflective glare is caused by a reflective light, and is the most common type of glare which also has the most effect on viewing comfort; this is because the angle of incident (the incident angle of light projecting onto the reading material) and the angle of reflection (the reflection angle of light reflecting into the eye) are equal, so that under normal viewing angle such type of glare is unavoidable.
Reflective glare makes the image blurry, reading difficult, causes eye strain, reduces reading efficiency, and even leads to soreness in the eyes and head-ache. According to research report, every four out of five workers suffer from discomfort of the eyes, and the majorities have symptoms of head-ache, fatigue, and lacrimation. According to statistics, among students with intense learning pressure, 55.9% of the interviewee expressed issues of eye soreness, lacrimation, and discomfort that lead to the undesirable action of rubbing one's tender eyes.
On the issue of how to improve the discomfort caused by reflective glare, prior art anti-glare structure of the current market can be grouped into three types: anti-glare film, anti-glare reflective mask, and light divider.
Therein firstly, the anti-glare film works by placing a reflective filter film at the emitting direction of the light source, so as to enable vertical light beam to pass through due to the reflective filter film, which converts horizontal glare into vertical light beam, and thereby reduces reflective glare. This type of reflective anti-glare film would often be coupled with a light transmitting optical strip, so as to spread the light uniformly through the light transmitting optical strip, and since the user would not see the light tube directly, thereby direct glare is reduced. However during the reflective process such reflective filter film causes some of the light to weaken, and therefore the efficiency of light emitting device and overall brightness is reduced.
Secondly, the anti-glare reflective mask works by placing a reflective mask outside the light source, so that the reflective mask may direct the light source to vertically project light upon a table surface, and ensures that the reflected light does not shine directly into a user's eyes, and thereby reduces reflective glare. Usually a diffuser is used in conjunction so as to convert direct light into diffused light, so that the user would not see the light tube directly and thereby reduces direct glare. However using the anti-glare reflective mask reduces light emitting range and increases the difficulty of design and production, furthermore the utilization of diffuser reduces the overall efficiency of light emitting device.
Lastly, the light divider works by placing a light dividing structure outside the light source, which not only prevents glare, but also adjusts light source into effective intensity, and so increases a light source's output efficiency. However using the light divider reduces light emitting range and the overall light efficiency of light emitting device.